Increased expression of TRPV1 in the trigeminal ganglion is involved in orofacial pain during experimental tooth movement in rats

<jats:p>To investigate whether transient receptor potential vanilloid type 1 (<jats:styled-content style="fixed-case">TRPV</jats:styled-content>1) is involved in pain induced by experimental tooth movement, experiments were performed in male <jats:styled-content style="fixed-case">S</jats:styled-content>prague‐<jats:styled-content style="fixed-case">D</jats:styled-content>awley rats weighing 200–250 g. Directed face‐grooming behavior was used to evaluate nocifensive behavior in rats during experimental tooth movement. The distribution of <jats:styled-content style="fixed-case">TRPV</jats:styled-content>1 in the trigeminal ganglion (<jats:styled-content style="fixed-case">TG</jats:styled-content>) was evaluated by immunohistochemistry, and its expression was detected by western blotting at several time points following the application of various magnitudes of force during tooth movement. Immunohistochemical analysis revealed that <jats:styled-content style="fixed-case">TRPV</jats:styled-content>1 was expressed in <jats:styled-content style="fixed-case">TG</jats:styled-content>, and its expression was increased after experimental tooth movement. Western blot results also showed that experimental tooth movement led to a statistically significant increase in expression of <jats:styled-content style="fixed-case">TRPV</jats:styled-content>1 protein in <jats:styled-content style="fixed-case">TG</jats:styled-content>. Meanwhile, the time spent on directed face‐grooming peaked on day 1 and thereafter showed a gradual decrease. In addition, both the change in <jats:styled-content style="fixed-case">TRPV</jats:styled-content>1 expression in the <jats:styled-content style="fixed-case">TG</jats:styled-content> and directed face‐grooming behavior were modulated in a force‐dependent manner and in concert with initial orthodontic pain responses. Our results reveal that <jats:styled-content style="fixed-case">TRPV</jats:styled-content>1 expression is modulated by experimental tooth movement and is involved in tooth‐movement pain.</jats:p>